The Status Of 5'-CpG Island Methylation Of FHIT Gene Is Associated With Gene Inactivation In Cervical Carcinomas

Cervical carcinoma is one of the most common malignant tumors in women. HPV infection has been identified as an important element in cervical carcinogenesis. But many women who had the HPV infection didn't develop this disease. Now, Fragile Histidine Triad (FHIT) gene, located at 3pl4.2, had been regarded as a candidate tumor suppressor gene which was associated with the development of esophageal breast bladder and kidney cancers. Most of cervical carcinomas had abnormal FHIT gene protein expression and high frequencies of aberrant transcriptional products were reported. FHIT gene abnormalities comprised loss of heterozygosity, homozygous deletions and the insertion of extra base sequences, et al. But still some scholars had the controversies about the inactivation mechanisms of this gene. For the point mutation was rare, some homozygous deletions just affected the introns and made exons more impact, and some one thought that only one of the alleles in FHIT gene had the loss of heterozygosity, the other one was normal, this would not have the adverse influences to FHIT gene transcription. So now it is still not clear about the mechanism of FHIT gene inactivation.Hypermethylation of cytosine in 5'CpG dinucleotides of RAR P16 DAPK, GSTPK CDH13> RASSFIA gene results in the inactivation of these genes. In addition, the 5'CpG island methylation of FHIT gene has been documented in prostate, breast, esophageal, and lung carcinomas, indicating its role in tumorigenesis. The promoter methylation could suppress the gene transcription through multiple ways. In this study, we had explored the status of 5'CpG island methylation andprotein expression of the FHIT gene and their clinic pathological associations in cervical tissues, to get the incidence of the promoter methylation of FHIT gene in cervical carcinomas and discuss the relationship between the methylation and the development of cervical carcinoma.Materials and MethodsForty primary cervical carcinomas were surgically removed and collected during 2001-2002 at Gynecological department of the First Affiliated Hospital of Zhengzhou University and Henan Tumor Hospital, China. Clinical information was obtained from the medical records. The average age of the patients was 46 years old (from 26 to 68) and none of them had received radiotherapy or chemotherapy. Among these tumors, 14 were stage I, 23 were stage II, 1 was stage III and 2 were stage IV. All the tumours were staged according to the International Federation of Gynecology and Obstetrics. Histologically, all the tumours were squamous cell carcinomas. 4 tumours were grade I, 19 grade II and 17 Grade III. In addition, 10 normal cervical epithelial samples were collected for this study. All the normal cervical specimens were obtained from patients operated for uterine leiomyoma. All the samples were divided into two portions. One was immediately frozen and stored at -80 . The other part was fixed in buffered formalin embedded in paraffin for routine pathological examination and immunohistochemistry.We used methylation-Specific PCR, immunohistochemistry staining to detect the promoter methylation in FHIT gene and FHIT protein expression status in a series of 40 cervical carcinomas and 10 normal cervical epithelial samples.SPSS 11.0 was performed to compare the data, and P value <0.05 was taken as statistical significance.Results1. 40%( 16/40 cases) of cervical cancer samples and 0%(0/10 cases) of normal cervical epithelial samples had the 5'CpG island methylation in FHIT gene. The incidence of methylation of FHIT gene was significantly higher in cervical carcinoma than in normal cervix(P<0.05).2. In cervical carcinoma, 14.28% cases of stage I and 56.52% cases of stage II had the 5'CpG island methylation in FHIT gene. The rate of promoter methylation of FHIT gene was increased with clinical stage between stage I and stage II(P<0.05).3. All the normal cervical epithelial samples (10/10) and 90% (36/40) of cervicalcarcinomas had the positive lanes by using the unmethylated...